The disclosures herein related generally to fluid turbines and more particularly to a ring valve for controlling the flow of motive fluid in a turbine.
Advances in the use of valves for controlling fluid flow in a turbine have included the use of an axial grid style valve to regulate flow. In U.S. Pat. No. 3,124,931, the flow at full or partial opening is directed to the downstream flow path. However, the axial orientation of the grid valve presents significant frictional force limitations. In addition, the axial orientation has an inherent clocking or phasing limitation which requires the use of relatively thick, and therefor inefficient, nozzle vane shapes.
In U.S. Pat. No. 5,383,763, a steam turbine includes a stationary channel body having channel inlets. The channel body has at least an adapter part in which the channel inlets are formed, and a basic part having steam channels formed therein being required for conducting steam to nozzles. The channel inlets connect control slits with the steam channels and are defined in accordance with an intended control characteristic.
In U.S. Pat. No. 5,409,351, at least one roller bearing race is disposed between the stationary channel body and the rotary slide outside the vicinity of the control slits and the channel inlets, for reducing rotational friction. At least one of the control slits and at least one of the channel inlets is disposed at each of at least two separate orbits. One of the channel inlets is opened, while others of the channel inlets to be opened remain closed, upon rotation of the rotary slide in a corresponding direction of rotation.
Both of the ""763 and ""351 patents are related in that they describe a grid valve system especially for steam turbine use, and both disclose a valve with radially positioned ports. The ""351 patent is primarily directed to the use of roller bearings in the valve to reduce pressure-induced friction. The ""763 patent is directed to a two piece channel body to limit the number of customized parts required. Both of these patents disclose a typical valve system that includes large plenum-like passages connecting the valve ports and traditional axially aligned nozzle vanes. The system disclosed in both of these patents requires as much as 180xc2x0 of rotation to fully open.
In U.S. Pat. No. 5,447,413, outer and inner endwall sections of a turbine are so profiled that, essentially, the flowpath is straight or flat in the direction of flow. The profiles are defined by lines of revolution about a centerline of the turbine, and shaped as projections upstream from blade tips or bases, tangent to such blade tips or bases, axially, and radially, conforming to a mean between convex and concave surfaces of the nozzle.
Therefore, what is needed is a valve for controlling the flow of motive fluid in a turbine which avoids these and further limitations of the prior art.
One embodiment, accordingly, provides a valve for controlling the flow of motive fluid in a turbine and includes a movable control valve ring, a valve body with flow passages, a nozzle ring and a valve actuator. To this end, an apparatus for controlling fluid flow includes a stationary valve body including a plurality of flow passages. Each passage extends from a passage inlet to a passage outlet. A control ring is movably mounted on the valve body adjacent to and radially outwardly from the passage inlets. The control ring includes a plurality of inlets formed therein. The openings are variably sized so that when the ring is moved relative to the valve body, the passage inlets are closed and opened in sequence.
Principle advantages of this embodiment include small valve actuator forces, single case penetration for actuation, less inlet loss, a more compact embodiment, fewer parts, and a symmetrical casing. Another important benefit is that nozzle ring ports that are partially open still accelerate the steam in a useful direction, thus enhancing performance.